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• 2. With the ruler in the fixed position directly read the depth to <br />water from the ruler at the point opposite the top of casing. <br />3. Record the reading to the nearest 0.1 foot on the Data <br />Collection Form. <br />A. 3. PRESSURE GAUGE READINGS <br />Where the water level in a well is above the top of the casing, a pressure <br />gauge is often used to measure the piezometric level in the well. The <br />pressure gauge may be permanently installed on the well or may have to be <br />temporarily installed for each measurement. It is important that the <br />"static" level be measured; therefore, every effort should be made to <br />minimize release of water (and pressure) from the well head prior to the <br />reading. In all cases the reading must be taken before the well head is <br />opened for sampling. .The procedure for measuring the pressure gauge is as <br />follows: <br />I. Install the pressure gauge, if none is already installed. <br />2. Allow pressure readin g to stabilize. <br />3. Read pressure (in psi ) from gauge. <br />4. Record reading to the nearest 0.5% of full gauge reading on the <br /> Data Collection Form. <br />5. Remove gauge and check that needle returns to zero pressure <br /> reading. If it does not, gauge is broken and must be replaced. <br /> If gauge is replaced, repeat process from step 1. <br />• A. 4. AIRLINE MEASUREMENTS <br />Airlines have been installed in wells in which direct measurement of water <br />levels would be difficult due to the presence of pumps or other <br />obstructions or in which the depth to the static water surface is large. <br />The airline works by using pressure (usually bottled nitrogen) to displace <br />water from the airline. The amount of pressure required to displace the <br />water is equal to the depth of water above the end of the airline. The <br />depth to water is equal to the total depth of the airline minus the <br />measured depth of water over the airline. Some installations have gauges <br />that read the pressure in psi (see attached Figure A-1) required to <br />displace the water while others read directly the depth to water in feet. <br />The procedure for taking a water level reading with an airline is as <br />follows: <br />I. If no airline manifold is permanently attached to the well, <br />attach the manifold by connecting the airline from the well to <br />the fitting below the large pressure gauge. <br />2. Connect the manifold to the tank. <br />3. Check that all valves on the manifold are shut and then open the <br />tank pressure valve. Do not look directly at a pressure gauge <br />when opening a valve because the gauge face is the most likely <br />point in the system to fail. <br />• <br />A-2 <br />